Method of grinding cutters



June 24, 1924. 1,499,094

. c. W. H BLOOD ET AL METHOD OF GRINDING CUTTERS Filed April 1. 192! izaizaf 2a 11.3 Z0063 law 'fZZJQkdiYOZd? M Patented June 24, 1924.

i STA TES :METI-IO'D OF GRINDING CU'IETERS.

Application filed April 1,

To aZZ whom it may concern:

Be it known that we, CHA-nLEs V; H. BLOOD and LOUIS T. MEDHOLDT, citizens of the United States, and residents of Vinthrop, in the county of Suffolk and State of Massachusetts, have invented an Improvement in Methods of Grinding Cutters, of which the following description, in connection with the accompanying drawings, is a specification, like letters on the drawings representing like parts.

ur present invention is an improvement in the forming of abrasive or grinding devices for use in sharpening knives or cutters, and particularly for subsequently j ointing the knives in a cutterhead'. An important object of the invention consists also in an improvement in the jointing operation itself. In the use of'high speed rotary cutters, such as the knives on planing machine cutters, the jointing operation has now becomeof recognized value, and the jointing of a straight edged cutter-head having a plurality of knives has proven of great benefit and is universally practiced. Our present invention is particularly valuable in enabling the sharpening and jointing of such moulding cutters to be accurately done. Furthermore, by our process we insure the accurate reproduction of any given contour of moulding cutter, and then enable a plw rality of such moulding cutters to be accurately jointed. Our invention contemplates the novel formation of the cutting abrasive or grinding material, by rendering it plastic, then conforming the abrasive accurately and exactly to the contour of a moulding cutter by subjecting the abrasive to the action of the cutter while the former is relatively soft and plastic, and then permitting it to harden, so that the contour thus accurately produced by the cutting knife itself is utilized and the jointing grinder for the same or similar cutter by which the contour in the abrasive was formed.

In carrying out our invention we provide aholder of suitable material, which can be readily cut, preferably wood, with a recess to receive the abrasive, either as a mixture which may be placed in the holder while soft, or a block or stick which may be fitted to the holder and softened, whereupon the soft 1921. Serial No. 457,701.

abrasive thus conformed to the contour of the cutting knife, is permitted to harden.

Such hardening can be done without removal of the block. lVhen so hardened the abrasive is ready to accurately grind or reproduce the contour thus imparted toit on subsequent cutting knives in grinding them, or in join-ting a plurality of such contoured knives in a cutterhead. Any suitable abrasive material may be utilized in carrying out our process, such as emery, carborund'um, or other abrasive material. Also a suitable binding agent can be utilized in forming this abrasive, the binding agent and abrasive being poured, packed or placed solidly within the mould and while still soft, subjected to the forming action on a cutter. lVehave found that Turnshemery, mixed with substantially equal parts of gum shellac and rosin, which are subjected to boiling before mixing, using about ten times the weight of binding material to the proportion of Turkish emery, makes an excellent abrasive which will remain 'so'ft for a sufficient length of time to permit the forming operation, i. e., moving the holder and soft abrasive contained therein into the path of a rotating cutter to determine the edge contour. This mass hardens very quickly and within from three to five minutes after the mixing and the filling in the mould, the abrasive can be subjected to the action of the rotating cutter toform its contour, and within from six toten minutes thereafter the mass will be sufficiently' hardened to constitute an eii 'ective grinding or jointing medium. Formerly dificulty was experienced in jointing moulding cutters, successive operations being necessary and upwards of one half an hour was often required to secure a reasonably correct jointing action on a plurality of moulding, cutters, whereas by our process the jointing is secured instantlyand as effectually as ointing straight edgec i cutters. Our employment of a holder or backing for the mass of plastic abrasive is important, said holder being capable of being formed and cut with .a knife during the forming operation, thus serving to protect the edges o-fth'e plastic material, while plastic, without injuring the cutting edgeof the forming cutter, is believed to be novel and we wish to claim this feature. Any

suitable holder to contain the abrasive may be used, but we find that an ordinary piece of wood, which cuts easily during the forming action and is inexpensive, will do this work satisfactorily. It is also feasible and within the scope of our invention to apply a mass of the abrasive onto an arbor and rotate the arbor while the abrasive is plastic, against a fixed or rotating cutter,'thus producing the grinding medium in rotary form with its contour made directly by the cutting knife which it is desired to oint, sharpen, or reproduce.

In order to cut and while plastic, it will be understood that we may either apply the abrasive to the holder before it hardens and immediately out it, or may apply a block, stick or piece of abrasive which is capable of being softened, to the holder and then soften it and cut as above explained. Such softening may be accomplished by loosening the binder in the abrasive material, with boiling water or any suitable agent to render the abrasive easily cut.

Referring to the drawings further illustrating a simple form of our invention,

7 Fig. 1 is a diagrammatic view partly in cross section of a cutterhead and mould carrying abrasive;

Fig. 2 is a side View of a mould and the abrasive out while the latter was relatively soft and plastic by a knife of the contour which it is desired subsequently to grind, to sharpen, to joint or to reproduce;

Fig. 3 is a view of the cutting end of a knife blade showing similar contour in reverse form;

Fig. 4 is a view of a modification of abrasive cutter.

In carrying out our invention any suitaable apparatus may be employed, that hereform the abrasive in illustrated being for explanatory purposes only and therefore being shown in simple and diagrammatic form. As illus- 1 a cutterhead 1 is mounted on a rotatable spindle 2, which cutterhead carries a cutting knife 3 in usual working position, i. e., exactly as the knife is presented to the work and as it is held in the rotating cutterhead. A plurality of such cutting knives are shown on the cutterhead 1 as illustrative of the jointing action, such additional cutters being shown at 4, 5 and 6. A wooden holder 7, preferably of rectangular form, is recessed in one edge as indicated at 8 to receive the artificial abrasive material 9, which is poured, packed or hammered firmly therein, while the holder 7 is square, as shown in dotted lines at 10, Fig. 2. This holder and the abrasive 9 may be mounted on a swinging arm 11 by bolts 12, which arm is pivoted at 18 to a standard 14, said arm being adapted for swinging movement radially toward and from the cutterhead 1. After the abrasive material 9 has been fitted within the recess in the wooden block 7, the block is then fixed to the arm 11 by the bolts 12 and within a suitable time, usually three or four minutes after the fitting of the abrasive material in the mould and while said abrasive material is still soft, the arm 11 is rocked downwardly, and a cutter 8, during rotation of the cutterhead 1, forms its edge contour 15 in the edge 16 of both mould 7 and abrasive material 9. This cutting edge may be of any contour desired, the cutter 3 reproducing accurately its contour in the soft mould 7 and abrasive 9. The arm 11 is then rocked upwardly and the abrasive allowed to harden. After a few minutes further time, the abrasive is suiiiciently hardened to constitute the grinding or jointing medium and can again be rocked downwardly for grinding or jointing a plurality of knives carried by the rotating cutterhead 1, as will be readily understood. It may be desired to bevel the edge portion of the wooden holder 7, as shown at 17, to afford better clearance, both for the cutter while cutting the abrasive, and for the abrasive, when hardened, while grinding the cutter.

In actual practice we find that the abrasive mixture, as above explained, is sufficiently tenacious to retain its position within the slot or recess 8 in the wood holder 7 during the preliminary forming and subsequent grinding actions, so that no separate retaining means are requisite.

It will be understood that the simple apparatus shown herein is for illustration only, and in actual work the movement of the holder 7, both for preliminary forming, and subsequent grinding, will be controlled by guides, screws, etc., when desired. In the modification is illustrated a wooden core and mass of abrasive 20, which is slowly turned while in peripheral contact with the cutting edge 15 of the cutter, while the abrasive is plastic. It is then allowed to harden, whereupon an abrasive surface is produced 'apable of grinding successive contours of the same pattern. Such a grinder may be mounted in a bracket 21 and connected with a pulley 22 to impart rotative movement thereto, to effect the grinding of successive contours on similar cutters.

It will be seen that in carrying out our invention a process of forming a grinder or grinding medium of suitable abrasive ma terial is shown capable of conforming the grinder with absolute accuracy to the uneven contour of a moulding cutter. Moreover, this accuracy in duplicating the moulding cutters contour is mechanically correct, not depending upon chance or skill of the workmen and automatically applies to any desired form or contour of cutting edge. Furthermore, the abrasive may be softened and reformed, cutting a new curve therein, a numa mass of plastic abrasive material to the her of times until it is entirely used up. It forming action of a cutter, moving the same will also be understood that any abrasive with respect to the path of movement of the mixture with capacity for plastic and hardcutter, permitting said cutter to shape the 0 ened conditions, may be employed in carrygrinding medium, then withdrawing said mg out our invention. grinding medium from the cutter and allow- Our invention is further described and deing the grinder to harden. fined in the form of claims as follows: 3. The improved process of forming l. The improved process of forming a grinding mediums suitable for the uneven 35 grinding medium for the uneven edges of edges of cutters, which consists in applying cutters, said medium consisting in a mass of a mass of plastic abrasive material to a abrasive material capable of being rendered wooden holder, which holder is capable of plastic, which consists in applying said abrabeing out by a forming cutter, moving the sive material to a holder and moving the said holder and plastic abrasive with respect 40 same while plastic, in the path of a cutter, to the path of movement of a forming cutter, permitting said cutter to shape the grinding permitting the said cutter to shape the medium, then withdrawing said grinding wooden holder and the plastic, then separatmedium from the path of movement of the ing said grinding medium and cutter and cutter and allowing the grinder to harden, allowing the grinder to harden, wherebysaid 45 while retained in said holder, and subsewooden holder supports the plastic abrasive quentlyformingadifferent grinding contour at the edge while plastic and during the by softening the abrasive and repeating the forming action of the cutter.

process. In testimony whereof, we have signed our The improved process of forming a names to this specification. grinding medium suitable for the uneven CHARLES 'VV. H. BLOOD.

edges of cutters, which consists in subjecting LOUIS T. MEDHOLDT. 

